The purpose of this study was to evaluate the effects of both marginal fit and cementing with different luting agents on the microleakage of all-ceramic crown systems. Thirty-six extracted upper central incisors were prepared for full-coverage crowns and were divided into three groups. Group 1: CAD/CAM-fabricated ZrO2, Group 2: Heat-pressed lithium-disilicate, and Group 3: Cast Cr-Co copings as the control group. Copings were made following standard techniques, and groups were assigned cementation with either self-adhesive resin cement (A) or glass-ionomer luting cement (B). The specimens were subjected to thermocycling, immersed in basic fuchsin solution, sectioned mesiodistally and buccolingually. The surface of each section was digitally photographed under a stereomicroscope. Microleakage was scored using a five-point scale, and the marginal gap was measured using image analysis software. Data were statistically analyzed using 2-way ANOVA, Kruskal-Wallis, and Mann-Whitney U tests (α: 0.05). The marginal discrepancy of each group was 82.7 ± 7 µm, 92.6 ± 4 µm and 96.5 ± 7 µm respectively. Group 1 showed significantly smaller gaps than Group 3 (P = 0.042). Self-adhesive resin cement (A) showed a lower level of microleakage than glass-ionomer luting cement (B) in all groups (P = 0.029). Microleakage scores of '0' were 83% for 1A, 50% for 1B, 50% for 2A, 16% for 2B, 33% for 3A and none for 3B. Marginal discrepancy and cement type both had significant effects on microleakage. Lower levels of microleakage were recorded with self-adhesive resin cement, while CAD/CAM-fabricated ZrO2 copings showed smaller marginal discrepancy and less microleakage in comparison to cast Cr-Co.

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A heat-pressed technique (IPS Empress, Ivoclar) has been described to construct single unit crowns, inlay/onlays and veneers using precerammed and precoloured glass-ceramic ingots. The aim of the study was to evaluate the strength of materials obtained using this technique. Strengths were determined by means of shell (disc rupture) tests. Seven groups of 10 specimens each were prepared with different combinations of core, incisal and glaze firing. Shell strength values of these seven groups varied between 167 +/- 18 and 81 +/- 9 MPa. After analysis, results showed that there was no statistical difference between groups when the core porcelain was in tension. However, there was a significant difference between those groups in which the lower surface was either core or incisal porcelain. The component thicknesses of the core and incisal materials did not change the strength of the complete specimen.

The microleakage beneath porcelain laminate veneers was investigated. The restoration margins were located according to the preparations made below or above CEJ of extracted maxillary central incisors. Vitadur N and Microbond porcelain materials were used to prepare laminate veneers. A light cured composite resin (Porcelite) and a light- and chemical-cured composite resin (Porcelite Dual Cure) were used as luting agents. The bonded specimens were thermocycled and by employing the standard dye penetration technique, the leakage was scored from cervical and incisal margins. Significantly greater microleakage was recorded at the dentine composite resin interfaces than at the enamel/composite interfaces. Statistically insignificant differences were observed with the use of the four cement/porcelain combinations studied.

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